This invention relates to electronic circuitry, and more particularly to circuitry that processes digital signals that may be disturbed by noise (i.e., electrical interference) from other sources in the system that includes the digital signal handling circuitry.
An example of a system that includes digital signal handling circuitry and that may also include other sources of electrical interference is a hand-held device with an image display and other features such as cellular telephone capabilities. The iPhone® cellular telephone available from Apple Inc. of Cupertino, Calif., is one such system. For example, in a product of this kind, large amounts of data must be passed from processor circuitry of the device to driver circuitry for the image display (e.g., the liquid crystal display or LCD) of the device. The digital signals transmitting this data typically have high data rates and relatively low voltage swing. These characteristics render these signals subject to corruption (errors) due to, for example, electrical interference (noise) from other sources in the system. Data errors in such signals can cause errors in the images that appear on the display. Such display errors can be visible (even highly visible) to the user of the device. They can be distracting or annoying to the user, and they may even have other more serious effects or consequences. It is therefore desirable to find ways to reduce the occurrence of such errors.
Although the discussion herein may most frequently mention circuitry that is handling data signals for driving a display, it will be understood that this is only an example, and that the invention is equally applicable to circuitry that is handling data signals for other purposes.